1. Field of the Invention
The present invention relates to a pedestrian protection apparatus, and a method of tuning a load characteristic of the apparatus. More particularly, the present invention relates to an improved configuration of a pedestrian protection apparatus that is installed on a lower front side of a vehicle and that protects the legs of a pedestrian by sweeping the legs in contact with lower parts of the legs when the front of the vehicle collides with or comes into contact with the legs, and to a method of advantageously tuning a load characteristic of the apparatus.
2. Description of the Related Art
Various types of protection apparatuses are conventionally installed on front, rear, or side faces of vehicles, such as automobiles, mainly in order to absorb a shock energy caused in a collision and to thereby protect the body of the vehicles and passengers. In recent years, apparatuses for protecting a pedestrian have been installed at the fronts of vehicles to protect the pedestrian when the front of the vehicles collide (comes into contact) with the pedestrian.
A so-called leg sweep member is a known pedestrian protection apparatus. The leg sweep member is installed inside or below a front bumper independently, and applies a reaction force to an impact load, which is inputted in a collision between the pedestrian and the front of the vehicle, to the lower parts of the legs of the pedestrian so that the lower parts of the legs are swept away (tripped) and the pedestrian falls down onto the vehicle. This advantageously reduces the angle of forced bending of the knees in an undesirable direction caused by the collision, minimizes the occurrence of injuries such as a bone fracture of a knee, and achieves protection and safety of the pedestrian.
For example, JP-A-2001-277963 discloses a leg sweep member in which a resin foam member and a beam are mounted in the lower part of the front of a vehicle. The resin foam member extends in a width direction of the vehicle such that at least a part thereof protrudes from the front of the vehicle, and the beam extends in the width direction of the vehicle and is in contact with the rear side of the resin foam member. JP-A-2004-25976 discloses a leg sweep member that is formed of, for example, a metal pipe, and that is fixed to the lower part of the front of a vehicle such as to extend in the width direction of the vehicle. However, both the leg sweep members disclosed in the above publications have disadvantages to be overcome. That is, in the former pedestrian protection apparatus including the resin foam member and the beam, the number of components is large. For this reason, the component cost is high, and it is troublesome to mount the apparatus. In contrast, in the latter pedestrian protection apparatus formed of a metal pipe, the weight thereof is inevitably high, and it is difficult to form the apparatus in a shape that conforms to the shape of the front of the vehicle.
In view of these circumstances, JP-A-2004-203183 proposes a pedestrian protection apparatus including a synthetic resin plate. The synthetic resin plate is fixed at a rear section to a vehicle such as to extend in the longitudinal direction of the vehicle and such that at least a portion of a front section thereof protrudes from the front of the vehicle. When the front of the vehicle collides with a pedestrian, the projecting portion of the front section protruding from the front of the vehicle comes into contact with lower parts of the legs of the pedestrian, and sweeps the legs away. In this known pedestrian protection apparatus, a plurality of flat ribs are disposed on one surface of the front section of the plate and formed in a lattice, and therefore, a high rigidity of the front section is ensured. Moreover, a section of the plate other than the front section is shaped like a flat plate extending in the longitudinal direction of the vehicle with a sufficient length so that the front section can protrude from the front of the vehicle.
In the pedestrian protection apparatus having the above-described configuration, the number of components is small. Moreover, since the plate, which partly protrudes from the front of the vehicle, is formed of easily formable synthetic resin, the pedestrian can be protected while effectively overcoming the disadvantages of the apparatus including the resin foam member and the beam, and the apparatus formed of a metal pipe. In addition, since the front section of the plate is highly rigid, it is prevented from being deformed by a shock caused by the contact with the legs of the pedestrian, or the amount of deformation is sufficiently reduced. Therefore, a reaction force to the impact load inputted to the plate efficiently acts on the legs of the pedestrian via the front section.
However, as the result of various tests and investigations, the present inventors found that the maximum value of the impact load inputted when the front section of the synthetic resin plate in the above pedestrian protection apparatus collided with the legs of a pedestrian did sometimes not reach a target value, that a reaction force required to sweep the legs away in the collision could not be ensured in this case, and that protection of the legs was insufficient.
In general, in a pedestrian protection apparatus installed at the front of the vehicle, the load characteristic is required to vary depending on the type of the vehicle, for example, to be optimized in accordance with the shape of the front of the vehicle and a shock-absorbing member of a front bumper mounted at the front of the vehicle together with the pedestrian protection apparatus so that a reaction force to an impact load applied in a collision between the legs of a pedestrian and the front of the vehicle sufficiently acts on the legs to reliably sweep the legs away, regardless of the type of the vehicle in which the apparatus is installed. However, in the known pedestrian protection apparatus having the above-described configuration, it is difficult to tune the load characteristic, so that it is difficult to optimize the same.